One such apparatus is for example known from U.S. Pat. No. 5,105,583, in which a machine for the deburring of internal and external burrs of metal workpieces is shown, in which the workpieces are moved in a horizontal transport plane relatively to the deburring machine. The deburring machine includes a planetary grinding head with a planet carrier which rotates around a vertical carrier axis at low speed. Inside the planet carrier three planet gears are mounted rotatably around vertical axes, which rotate at high speeds when the planetary grinding head is driven. Brushes, whose bristles are engaged vertically against the surface of the workpiece, are attached to the planetary gears.
An apparatus of the afore-mentioned kind not only serves for deburring, but also for removing oxide layers from cutting areas, which oxide layers are formed e.g. during the cutting of metal sheet plate to size with the help of laser beams or during autogenous cutting. Since such burrs usually protrude vertically from the workpiece surface, they will be removed during processing of said surface, while the cuffing areas extend perpendicularly to said surface and require processing in a processing plane perpendicular to the workpiece surface processing plane.
In order to be able to process the workpiece simultaneously in said processing planes which are perpendicular to each other, the brushes, which in an apparatus of the afore-mentioned kind are generally engaged against the workpiece surface, have to be sufficiently soft and yielding to reach both the surface and the cutting areas of the workpiece. The thicker the metal sheet plate to be processed is, the softer the bristles of the grinding brushes need to be so as to cover the entire cutting area, respectively, generally speaking, the edges of a workpiece.
However, the bristles may not exhibit any desired degree of softness, since their abrasive effect might become too small. Since it has recently become possible to cut metal sheet plate of increasing thickness to size by means of a laser, it is no longer possible to perform comprehensive processing of the edges of a workpiece by means of a known apparatus of the afore-mentioned type with satisfactory efficiency.
In the above-mentioned U.S. Pat. No. 5,105,583 it is suggested not to arrange the carrier spindle in an exact vertical direction (and thus not orthogonally to the transport plane, at variance from the wording of the preamble), but to tilt its upper end somewhat in the workpiece feeding direction which results in a higher pressure being exercised on the front face of the workpiece, which in turn causes an increase in the abrasive effect on the workpiece front face, while the abrasive effect on the lateral edges does not increase and the abrasive effect on the workpiece rear face even decreases.
It is an object of the present invention to provide an apparatus of the afore-mentioned kind which allows comprehensive and efficient processing of the edges of a workpiece also for comparatively thick workpieces.
This object is solved by an apparatus according to the present invention. This enables the bristles to process different portions of the workpiece edges in accordance with their respective distance to the transport plane. Thus, by selecting the distances of the bristles from the transport plane in a suitable manner, the entire width of the workpiece edges (i.e. the entire thickness of the workpiece) can be processed, while there is no need for using especially soft bristles. Thus, it is possible to achieve a far greater abrasive effect with the apparatus according to the present invention than with known apparatus.
Varying distances between the ends of the bristles and the transport plane can be reached in different ways. In a preferred embodiment of the invention the bristles on the individual grinding brushes differ in length. In another preferred embodiment the brush bodies are tilted with respect to the transport plane. In both cases, a good abrasive effect on the entire width of the workpiece edges is achieved, while the respective distances between the ends of the single bristles and the transport plane do not change during the rotation of the grinding brush. Since the bristles are arranged at different distances to the transport plane, however, they wear off unevenly.
In an improved embodiment, the brush bodies are tilted with respect to the transport plane, while the brush axes extend in an orthogonal direction with respect to the brush bodies. This means that the distance between each single bristle and the transport plane changes as the brush rotates around its brush axis. The brush itself can be rotationally symmetric with respect to the brush axis and thus wears off evenly.
Preferably, the distances between the ends of the bristles and the transport plane differ by up to 1 to 2 cm. In an advantageous embodiment the apparatus includes several planetary heads which are arranged in two rows extending transversely with respect to the workpiece transport direction with the rows being arranged one behind the other in the workpiece feed direction and with the two rows of planetary heads being offset towards each other transversely with respect to the workpiece transport direction such that the planetary heads of one row—when viewed in the workpiece transport direction—close the gaps between the planetary heads of the other row. By using such an arrangement also big workpieces, and in particular broad metal sheets, can be processed.
A further improvement can be achieved by using different types of bristles. Thus the bristles of at least one of the grinding brushes can differ from the bristles of the other grinding brushes in their material characteristics, structure, texture, hardness, thickness and/or trimming length. The different types of bristles may necessitate a different infeed of the grinding brushes in the direction of the workpiece in order to reach the desired results and may moreover exhibit different wear behaviour during their useful life. For this reason it is advantageous if the infeed of at least some of the grinding brushes can be regulated individually. It is also possible to control the infeed of sets of grinding brushes of the same type, for which purpose use may be made of a support element for grinding brushes of the same type which is centrally adjustable. In an alternative solution all grinding brushes are arranged within a common support element such that they can be axially adjusted with sets of like grinding brushes being adjustable via a common operating device.